332 



CHAPTER II. 

 PROBLEM OF THE VIBRATIONS OF STRINGS. 



THAT the continuation of sound depends on a 

 continued minute and rapid motion, a shaking 

 or trembling, of the parts of the sounding body, 

 was soon seen. Thus Bacon says 1 , "The duration 

 of the sound of a bell or a string when struck, 

 which appears to be prolonged and gradually ex- 

 tinguished, does not proceed from the first per- 

 cussion; but the trepidation of the body struck 

 perpetually generates a new sound. For if that 

 trepidation be prevented, and the bell or string be 

 stopped, the sound soon dies : as in spinets, as soon 

 as the spine is let fall so as to touch the string, 

 the sound ceases." In the case of a stretched 

 string, it is not difficult to perceive that the mo- 

 tion is a motion back and forwards across the 

 straight line which the string occupies when at 

 rest. The further examination of the quantitative 

 circumstances of this oscillatory motion was an 

 obvious problem ; and especially after oscillations, 

 though of another kind, (those of a pendulous body,) 

 had attracted attention, as they had done in the 

 school of Galileo. Mersenne, one of the promul- 

 gators of Galileo's philosophy in France, is the first 



1 Hist. Son. et And. vol. ix. p. Jl. 



